I am opening this topic because I want to build an altimeter for a friend that is a skydiver. My experience with arduino and esp8266 is not so wonderful, what I want to say I build in the past a lot of small projects but never a project that is so complex.
just one note: you need at least 2 pressure sensors for altitude, as the object of interest is moving and you have to work around aerodynamic effects (google for pitot tube). what about GPS for height estimate?
My experience of sky diving is that I have done it once and survived. I didn't have an altimeter or any other instrumentation, although I did have a radio receiver and someone on the ground telling me what to do. It seems to me that if a faulty altimeter were telling me I have 10000 feet left to fall and my eyes were telling me I was getting close to going splat, then I'd take the judgement of my eyes over the information coming from some electronics. I would imagine that as long as the person using the device knows its limitations and knows that it cannot be regarded as a safety critical piece of equipment then that would be OK.
Comment from an experienced sky diver would be interesting.
Sorry to pile-on but I agree with everybody else...
Altimeter for skydiving
When I saw that title the first thing that came to mind was, "Are you nuts?".
I am opening this topic because I want to build an altimeter for a friend that is a skydiver. My experience with arduino and esp8266 is not so wonderful, what I want to say I build in the past a lot of small projects but never a project that is so complex.
Are you nuts?
...I know some people build their own airplanes but (hopefully) you wouldn't build one for someone else. And, you probably wouldn't build an airplane if your experience building cars (or other mechanical things) was "not so wonderful".
Soo, what are you all saying is that I should buy an altimeter that was made with an atmega 328p and it cost @600$ ?
My ideea was to build one with more features, also my friend always has one mechanical altimeter attached on his arm, I do not know why are you all so scarred of this topic.
Having done over 1300 free fall skydives I think I may be qualified to comment on this topic. I used to have 3 different altitude sensors all based on air pressure. A wrist mounted altimeter with an analogue readout. An audible altimeter which was set to give an continuous bleep when I reached a set altitude and rate of descent. An CYPRES altimeter to open my reserve parachute if I was not under canopy by 1,500 ft. All three altimeters were zeroed each time I put on the parachute so that they measured altitude relative to the drop zone altitude.
Only the wrist mount altimeter was mandated; the other 2 were optional (this may have changed now). The wrist mount display had three bands. White for above 3000ft, yellow for between 2000 and 3000ft and red for below 2000 ft. Being analogue and colour coded made it easy to get the important information without having to spend too much time looking at the altimeter.
A typical free fall starts at about 12,000ft and one gets to terminal velocity of about 120 mph after about 15 seconds. The total free fall time is about 60 seconds. The only information one has time to deal with is one's altitude and I would be very very uncomfortable with an altimeter display that was cluttered by superfluous information. In the UK, one has to deploy one's main canopy so as to be under canopy by 2,000 ft. This then allows one to revert to plan B (using one's reserve) if the main canopy fails to deploy properly.
I can see little advantage to having more information than altitude available during free fall.
stowite:
I can see little advantage to having more information than altitude available during free fall.
It might even be considered a disadvantage; my dive computer gathers and stores more information that it displays - you can extract it after the dive if you care.
Water temperature is one thing in this category; the designer's argument is that it is best to give you the information you need to dive safely without causing possible confusion with additional clutter. And besides: "you know when you're cold".
(Which is almost as deep as the Mariana Trench...)